1. Field of the Invention
The present invention relates to Internet Protocol (IP) networks, and more particularly, to methods and systems for congestion avoidance in IP backbone networks.
2. Background of the Art
A communications network generally includes a plurality of nodes interconnected by transmission links (or “links”), which are defined by a specific bandwidth (or capacity). In an IP network, a source node transmits data in the form of packets to a destination node through a route, which may traverse zero or more nodes (i.e., switches, routers, bridges, etc.) between the source node and the destination node. The packets may include any type of digitized information, including audio, computer data, video, multimedia, etc. There are several protocols that IP networks, for example the Internet, generally use for transporting data between nodes in the network. One such protocol is the Transmission Control Protocol (TCP).
A TCP/IP network uses a congestion control technique known as Congestion Avoidance Algorithm (CAA). In such a network, nodes use packet losses in the network as congestion indicators and, based on these indicators, adjust their rate of packet transmission. An end node maintains a congestion window based on the congestion indicators that it receives from the network. The node maintains its congestion window size below a maximum segment size per round trip time, and reduces the congestion window size by half each time the source node receives a congestion indicator.
However, random packet losses, which generally have relatively short durations, can cause significant throughput degradation for network services operating in a high bandwidth-delay product regime. Furthermore, in wide area networks, because of long propagation delays, a node cannot adequately track congestions occurring at, for example, a destination node. As a result, the node may significantly decrease its congestion window size, even though the congestion at the destination node no longer exists, resulting in an inefficient allocation and use of network capacity.
Thus, it is desirable to have a method and system for addressing the above and other disadvantages of the existing congestion control avoidance methods for bursty traffic in IP networks.